CS08 Biogeochemical Cycles
Date: Tuesday, June 11, 2002
Location: Poster Session - VCC
 
KaoSJ, Environmental Change Research Program, Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan POC, sjkao@earth.sinica.edu.tw
Liu, K, K, Insititute of Oceanography, National Taiwan University, Taipei, Taiwan POC, kkliu@ccms.ntu.edu.tw
 
NITROGEN YIELD IN A PARTIALLY CULTIVATED SUBTROPICAL MOUNTAINOUS WATERSHED IN TAIWAN
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Three species of dissolved inorganic nitrogen (DIN; NO3, NO2 and NH4) were monitored in the Lanyang-Hsi, a subtropical mountainous watershed at northeastern Taiwan, during dry and wet seasons. In both the cultivated main channel and uncultivated tributary areas, NO3 was the most abundant species, which accounted for >80 % of total DIN, while NH4 and NO2 was <15 % and 5 % of DIN, respectively. Agricultural activity is likely to be responsible for contrasting spatial pattern showing that NO3 concentrations (13 to 246 uM) and estimated DIN yields (1300 to 3800 kgN/km2/y) in the main channel were higher and more variable than those (9-38 uM for NO3 and 660+120 kgN/km2/y for DIN yield) of the uncultivated tributaries. From reported precipitation chemistry data, the atmospheric DIN input (>1900 kgN/km2/y) was 3 times higher than DIN yield of uncultivated watersheds suggesting a high capacity for DIN retention in the uncultivated tributary system. Results suggest that undisturbed N cycling in the Lanyang-Hsi watershed is more like that in temperate watersheds rather than that in tropical watersheds showing generally low N retention.